Electron-discharge device



Jui? 3Q, E929- F. L. HUNTER, JR

ELECTRON DISCHARGE DEVICE Filed April 5, 1924 zo A 3a PILAMEHT Powsn n1 WAT-rs n JNVENTOR Frederick L. Huzzer, Ji'.

NEY

Parenteel July 3o, 1929.

, y 1,722,462;v UNITED STATES PATENT QFFICE.'

FREDERICK L. HUNTER, JR., 0F TOWACO, NEW JERSEY, ASSIGNOE TO DE FOREST RADIO TELEPHONE & TELEGRAPH C0., 0F JERSEY CITY, NEW JERSEY, 'A COR- POBATION 0F DELAWARE.

ELECTBON-DISCHARGE DEVICE.

This invention relates to electron discharge devices and more particularly to the construction of filaments for use in electron discharge devices.

The objects of the invention are to provide means for utilizing space charge for regulating emission in electron discharge devices; to increase the ratel of emission from a lilament of given length; to increase the surface from which emission is to be obtained; to secure the increase in the rate f emission without raising Athe temperature of the filament over the proper or usual temperature; to provide a filament which will be durable and efficient; to secure simplicity of construction and operation, and to obtain other advantages and results asfmay brought out in the fol-v' lowing description.

Referring to the accompanying drawing 1n which like numerals of referencevindicates 4'similar parts throughout the several views;

Figure l is an elevation of an electron discharge device with parrts broken away so as to show my improved filament mounted). therein; A

Figure 2 is a longitudinal elevation of the preferred embodiment of my invention with the end tabs in section;

Figure 3 is a similar view of a modified con-` struction of filament; c

Figure 4 is an elevation of a still further modified construction of filament; Figure 5 is-a cross sectional view of the filament shown in igure 2;

Figure 6V is a s' ar cross sectional view Y of the filament shown in Figure 3;

. 4; and

Figure 7 is a cross sectional view of the filament shown in Figure 4g;

Figure 8 is a cross sectional view of a further modied construction of filament an elevation of which would be the same asFigure Figure 9 is a plotted curve showing the relation of emission of a single wireflament and 'a multiple wire filament constructed, in` accordance'with the present invention.

In the art of radiant energy, andparticularly in connection with the electron dis- `charge devices employed therein both for receiving,`amplifying and transmitting energy,I

it has been found 'desirable to obtainill certain instances a reserve supply of emitted electrons in order to meetthe demands of an increased current in the output circuit. In

the emitting order to obtain this reserve supply,'I utilize the electro-physical attribute of `electrons'.

that electrons repel each other. In other' words, I construct a filament so that when an abnormal demand is made upon the electron discharge device there will be an excess su ply of electrons which have been held in suspension by the repellent action of the electrons themselves. It is not practical to obtain this mcreased emission in a given size of lilament by an increase in temperature, because a filament, in order to have a long life, should be heated only to` its proper temperature. Heating thoriated or analogous filaments beyond proper temperature will not obtain temperature saturation, but emission goes on up until the thorium boils olf. 'In Figure 9 I have plotted the emission of an ordinary thoriated filament on curve A-B. On the horizontal axis I have plotted the filament power or` its equivalent, temperature, and on the vertical axis I have plotted the hi h free` quency output current. It is to be o served that since the filament is not one which is adapted to keep the electrons in reserve by space charge, electrons are used as fast as they can be emitted, but that not being fast enough material' boils off andy thorium emission ceases altogether at point B.

Obviously, thereforez it is not practical to obtain increased emisslon by increasing the temperature, but ,itispracticah I find, to increase the emission-by increasing the emittmg surface or by increasing the reserve supply of electrons, or both. `For purposes of lcomplete disclosure, I have shown a filament Peo` is increased, but it is to be understood that I do not confine myself to both being employed together.

' Where the input of filament power is 'limited and the temperature is speciiied, together with a certain requirement for output current, obviously an increase of emission cannot be obtained by an increase ofM temperature or power in the filament, but must be obtained by having emitted electrons in reserve. T oo rapid emission of uncontrolled electrons is not only undesirable but -harmful and it is therefore important to control the emission of the reserve supply which is accomplished by space charge or repellantac-v tion of the electrons for each other. I proy the horizontal axis so that aconstant output current 1s obtained for a considerable .varia- 2ly j 1,722,468

l vide a device wherein, at temperature satura Vtlon, the space charge is so great that further vemlssion 1s ractically Astopped .until there is a demand or further electrons. devicel constructed in accordance with my invention w1ll develop a curve suchA as C-D-fE, the `portion D-E being substantially parallel to tion of lament ower or temperature. It will be appreciated that the filament power is supplemented or' subtracted from by the plate current according. to which way the filament current is iowing. That is to say, when the filament current and plate current 'are owinlin the same direction`in the ila- `ment the creased, butwhen the filament current andv ament current is materially inplate current-are flowing in opposite direcadvantage of the increased surface of all of t. only the wires for emitting purposes rather than just the surface of a single wire the size of the filament. Obviously, by' intertwining,'weav ing or braiding, the wires, the filament is not considerable length of the constituent wires.

' Such a filament will accordingly enable a very much increased rate lof emission to be obtained because of the increase in the emittin A surface of the filament. Y.

referably the filament 1 is hollow or tubu- -lar as clearly shown in Figure 5,- this structure securing an increase in the space charge.

` taining .space charge b I do not wish it to be understood, however,

`that I limit m self to a woven filament which y invention contemplates oba filament having a. roughened vsurface an also by hollow ilament of any kind.` For illustrative purposes I have shown a hollow lilament and a woven is hollow.-

filament as one and the same. It is to be observed that electrons emitted from the outside or exposed portions of the.. tubular filament vand those emitted from theinside surface ofthe tubular filament are all of the saiepolarity.- Asa result, the electrons outside. will. have 'a repelling action with the respect to those-inside, andI .therefore believe have a tendency to prevent'theelectronsVV inside from coming out. v However, when' there is a demand upon the filament for elec- .trons which the exterior surface is unable to supply, the repelling action of the outside electrons is materially reduced` because there rough on its surface, but utilizes a very cylindrical and preventing separation.

they are actively attracted away-from the filament and' the sameattraction is operating upon the electrons in the filament. The reserve suppl yof the electrons accordingly meets the a normal demand without necesthetilament.

yI preferably construct a filament such that the total emission -at the operating Atem rature. is greatly in excess of Jthe norma demand, but so re ulate'the space charge that the excess is hel in reserve. By this means,

the uncontrolled' or. unrepressed emission 1s practically constant over a considerable range of temperature as may be observed byreference to the portion of curve. This` eiect is known as temperature saturation. .As a concrete example, assuming the filament to Abe normally operated by an input of 9to 10 volts, I arrange that the` uncontrolled emission is suflicient for operation at 9' volts.

From 9 volts to 10 volts and beyond, the deviceis operatingin the temperature saturation-part of the curve, that is, the horizontal part ofsthe curve shown in i taining a practically constant electron llow from 9 volts and above.

Instead of Weaving or braidin the wires forming the filament the group o wires may be twisted together as illustrated in connec-4 tion with filament 2 in Figure 3 and .6, or may Figure 9, thus ob- `.are not onl less electrons there, vbut because sitating any increase in thextemperature `of be extended side by side in parallel relation as shown in Figures 4, 7 and 8, although-I have noted the results are not so good as 1n the woven or braided filament. In Fi res 4 and 7 I have shown a filament 3 wherein the parallel wires-forming the filament arev grouped or bunched together leaving only such hollow spaces as may exist`between'the several wires. In Figure 8 I have shown parallel wires forming the filament 4. which are assembled in a bular o r hollow filament. Obviously the wires constituting-the twisted filament 2 of Figure 3 may likewise be grouped to substantially fill the cross sectional area of the filament as shown, or may be arranged in a cylin.- drical groupings() as to form a hollowl filament, the cross sectional view of which will be the same as Figure 8. I i

welded for securing good electrical contact Any suitable material may be used for the end tabs 5, and any suitable emitting material may be nsed articular materials emp oyed not being a eature;l of the present invention.

The 'iilament described above may be eni-l electron discharge device. It

ployed in anv d, that in the present disclosure may-be note I have shown'the same in an ordinary receiv` ing tube 6, it not being considered necessary The filaments are preferably introduced in' to the tubular `end Ytabs 5 to which they are arrangement so as to obtain a tu the lilament, the

than the usual ilament employed in receivingy tubes, however, adapts the invention to transmitting tubes wherein a larger filament is employed and wherein a greater current is used, but the principle of the invention is applicable to any electron discharge device.

While I have expounded upon what I believe to be the theory of operation of my improved electron discharge device, it isnot mypurpose to restrict the invention to any Y theory f operation, such having been given to enab eothers to have a better understanding ofthe invention. Obviously other detail changes and modications maybe made in the :manufacture and use of my improved electron discharge device, and I dovnot wish to be understood as limiting myself to the eX- act structure shown except as set forth in the following claims when construed. in vthe light of the priorl art. v.

Havingthus described my invention, I claim/z l; A hollow electron emissive filament composed of a plurality of longitudinal wires.

2. Arf electron emissive iilament for use in an electron discharge device comprising na plurality of longitudinal wires in a cylindrical group to enclose and store a reserve electron space charge.

FREDERICK L. HUNTER, JR. 

